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Mesoporous 55 wt.% Ni/MgO and group VIB metal (Cr, Mo or W)-doped catalysts were prepared using the facile "one-pot" evaporation-induced self-assembly in ethanol and wetness impregnation methods, respectively. Physicochemical properties of the as-prepared catalysts were characterized by means of the BET, XRD, SEM, TEM, HAADF, XPS, H2-TPR, TPO, and Raman techniques. The doping of Cr to 55 wt% Ni/MgO improved catalytic activity and stability for the decomposition of methane under harsh reaction conditions. The maximal initial methane conversions of 80, 87, and 75% were achieved over the 55 wt.% Ni−xCr/MgO (denoted as 55Ni−xCr/MgO; x = 5, 10, and 15 wt.%) at 675 oC and GHSV = 48,000 mL/(g h), respectively. It is concluded that the high catalytic efficiency of the Cr-doped sample in methane decomposition was associated with its high surface area, high oxygen adspecies concentration, and good low-temperature reducibility. In addition, multi-walled carbon filaments with metal-encapsulated carbon particles were deposited on the Cr-doped catalysts, and the ordered carbon filaments with different diameters and good crystallinity were produced on the surface of the 55Ni−10Cr/MgO catalyst.

Single-atom catalysts are a kind of promising catalytic materials that can use the precious metal more efficiently. The KIT-6-templaing method was adopted to obtain three-dimensionally ordered mesoporous iron oxide (meso-Fe2O3). The meso-Fe2O3-supported single-atom Pt with a loading of x wt% (xPt1/meso-Fe2O3, x = 0.08, 0.15, and 0.25) catalysts were synthesized via a polyvinyl alcohol-protected reduction route. The 0.25 Pt1/meso-Fe2O3 sample showed much better catalytic activity than the meso-Fe2O3-supported Pt nanoparticle (0.25 PtNP/meso-Fe2O3) sample for benzene combustion, with the temperatures T10%, T50%, and T90% (corresponding to benzene conversions of 10, 50, and 90%) were 164, 186, and 198 °C at a space velocity of 20,000 mL/(g h), respectively. The TOFPt (2.69 s−1) obtained over 0.25 Pt1/meso-Fe2O3 at 160 °C was much higher than that (1.16 s−1) obtained over the 0.25 PtNP/meso-Fe2O3 sample at 160 °C. Furthermore, the 0.25 Pt1/meso-Fe2O3 and 0.15Pt1/meso-Fe2O3 samples exhibited better water-resistant ability than the 0.25 PtNP/meso-Fe2O3 sample, which was possibly due to formation of the active radicals and decomposition of carbonates in the presence of moisture. In situ DRIFTS results demonstrate that the phenolate and benzoquinone as well as cyclohexanone and maleate were the main intermediates in the oxidation of benzene. The good stability of the 0.15Pt1/meso-Fe2O3 and 0.25 Pt1/meso-Fe2O3 samples was associated with the strong interaction between Pt and meso-Fe2O3.

Balancing the NH3 selective catalytic reduction (NH3-SCR) and catalytic oxidation performance is difficult but necessary for the synergistic elimination of NOx and chlorine-containing volatile organic compounds (CVOCs). We herein unveiled that electronic structure tailoring of the applied catalyst was an efficient pathway for balancing the catalytic behaviors in the NH3-SCR of NO and chlorobenzene catalytic oxidation (CBCO). Specifically, environmentally friendly CeO2 substituted by low valent Al3+ exhibited better NH3-SCR of NO and CBCO activity in comparison with the CeO2 sample without doping. Detailed characterizations and theoretical simulations revealed that the strong dopant-oxide pairs in the CeO2 with Al3+ doping significantly tailored the electronic structure of O 2p states, enhancing the amount of Lewis acid sites and promoting the ability of lattice oxygen to act as an oxidizing agent, thereby leading to superior performance for the synergistic elimination of NO/CB. The counterpart with substitution of high valent Ta5+ showed an opposite trend, due to that Ta5+ donated more electrons to the coordination oxygen than Ce4+ inhibiting lattice oxygen separating from the surface of the catalyst, and Lewis base sites were formed.

Polymeric carbon nitride (C3N4) is a very attractive candidate to produce photocatalytic hydrogen peroxide (H2O2) due to its low-cost, metal-free characteristics. However, the low efficiency would limit its development to higher yields because of insufficient light absorption and electron-hole separation. Here, we developed a simple method to anchor CN quantum dots (QDs) onto g-C3N4 nanosheets to form a homojunction structure (HJ-C3N4), which could improve photocatalytic performance largely without introducing metal elements. Its superior efficiency is a result of the band alignment by the homojunction structure providing excellent electron-hole separation and QDs providing suppressed recombination. Simultaneously, the light responsiveness of QDs endows a wide spectrum-responsive adsorption and enhances the adsorption intensity. The H2O2 yield of the HJ-C3N4 reached 115 μmol·L−1·h−1 in pure water by visible light, which has an 8.6x higher production than g-C3N4 nanosheets. The material design of 0D/2D homojunction could be extended to other materials with specific band alignment.

Ammonia (NH3) as an important precursor to form atmospheric fine particles and secondary inorganic aerosols, should be strictly controlled. Photocatalysis has provided a facile and an effective way to eliminate NH3 pollution under mild conditions, whereas the undesirable products, such as NO, NO2 would be generated during the reaction and the mechanism remains unclear. In this study, F or Pt modified TiO2 were explored to reduce the formation of NOx during photocatalytic oxidation of low-concentration NH3, and its photocatalytic activity, selectivity and mechanism of NH3 conversion were systematically studied. Results indicate that surface fluorination on TiO2 contribute to the reduction of noxious NOx, especially for NO2, since the modified TiO2 achieved enhanced adsorption of NH3 and strong electron-trapping ability, which can retard the recombination of photo-generated electrons and holes. In addition, the deposition of Pt could further extend the lifetime of the electron-hole pairs by strongly capture the electron, and enhance the oxidation of NH3 into nitrates and nitrites species. From the in-situ DRIFT spectroscopy and XPS results, we can deduce that reactive amino radical (•NH2) would be formed on TiO2 under photoirradiation after the adsorption of NH3 on Lewis acid cites. The formed •NH2 can react with reactive oxygen species in the presence of H2O, and produce NOx and HNOx. By both enhancing the adsorption of NH3 and separation efficiency of electron-hole pairs, the presence of F and Pt modification on the TiO2 changes the photocatalytic pathway of NH3 conversion. The proposed selective oxidation mechanism may offer a novel insight into the photocatalytic oxidation of atmospheric NH3 on other metal oxide with surface modification and can be broadly employed in air pollution control in indoor environments.

Leaf-like monoclinic BiVO4 and yCoxPd/BiVO4 (CoxPd loading (y) = 0.060 − 0.092 wt%; Co/Pd molar ratio (x) = 0.26 − 1.70) photocatalysts were prepared using the hydrothermal and polyvinyl alcohol-protected reduction methods, respectively. The Co−Pd nanoparticles (NPs) with a size of 4–6 nm were well dispersed on the surface of leaf-like BiVO4. The bimetallic Co−Pd-loaded BiVO4 samples performed much better than the monometallic Co- or Pd-loaded counterpart, with the 0.062Co1.70Pd/BiVO4 sample showing the best photocatalytic performance (the time for 90% phenol removal was 3 h under visible light irradiation) and good photocatalytic stability. The pseudo-first-order reaction rate constants (0.4753 − 0.8367 h−1) obtained over yCoxPd/BiVO4 were much higher than those (0.0619 − 0.3788 h−1) obtained over BiVO4, 0.058Co/BiVO4, and 0.083Pd/BiVO4, with the 0.062Co1.70Pd/BiVO4 sample possessing the highest rate constant. In-depth investigations of X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and photoelectrochemical measurements reveal that high dispersion of bimetallic Co–Pd NPs increased the surface Pd0 and superoxide anion radical concentrations and suppressed the recombination of photoinduced electrons and holes (hence enhancing the photocatalytic activity of yCoxPd/BiVO4). The partial deactivation of the 0.062Co1.70Pd/BiVO4 sample after 15 h of three recycle tests was mainly due to the decrease in adsorbed oxygen species concentration. In addition, the possible photocatalytic phenol degradation mechanism over the 0.062Co1.70Pd/BiVO4 sample was also proposed. We believe that the BiVO4-supported Co–Pd NPs have promising applications for the photocatalytic elimination of organic pollutants in wastewater.

Volatile organic compounds (VOCs) are the crucial precursors to the formation of fine particulate matter and photochemical smog. Photocatalytic oxidation (PCO) under vacuum ultraviolet (VUV) irradiation has attracted increasing interest for VOCs degradation owing to its strong oxidation capability and excellent stability. However, the generation of O3 from VUV irradiation causes secondary pollution and needs to be addressed. In this study, the Mn doped mesoporous TiO2 (Mn/meso-TiO2) was developed and first combined with VUV irradiation to remove O3 as well as enhance benzene degradation via O3-assited catalytic oxidation. Results indicate that the Mn doped TiO2 exhibited a much higher benzene removal efficiency (82%) than undoped one (70%) and commercial TiO2 P25 (48%). The O3 by-product can be completely eliminated by Mn/meso-TiO2 and contributed to benzene removal efficiency of about 34%. The excellent performance was attributed to the formation of highly reactive oxidizing species such as O(1D), O(3P), hydroxyl radicals ( OH) via catalytic decomposition of O3 over oxygen vacancy sites of Mn oxides. Mn/meso-TiO2 cooperated well with VUV and such a VUV-PCO process is very promising for VOCs degradation.

In this work, Fe2O3 supported single atom Pt (x Pt1/Fe2O3, x = 0.25 and 0.5 wt%) catalysts (SACs) are synthesized via a novel and simple impregnation-pyrolysis method. HAADF-STEM images show that Pt is atomically dispersed on the surface of Fe2O3. All samples exhibit good light-thermal conversion efficiency, which can increase the surface temperature of catalysts to 210 °C. The 0.5 Pt1/Fe2O3 exhibits the best photothermal catalytic performance (the toluene conversion and CO2 yield are 95 % and 87 %, respectively) for toluene oxidation under the irradiation of simulated sunlight with light intensity of 720 mW/cm2, which is attributed to its good light-thermal conversion efficiency and low temperature reducibility. The Vis-IR light plays a critical role in the photothermal catalytic oxidation of toluene in the whole solar spectrum. Furthermore, the possible photothermal catalytic reaction pathway of toluene oxidation is proposed based on the TD-GC/MS and in-situ DRIFTS experiments.

In this work, we first used the oil-phase co-reduction strategy to synthesize the RuxMny (Mn/Ru molar ratio (y/x) = 7 : 20, 21 : 25, and 17 : 10) intermetallic compounds, then used the KIT-6-templeting method to prepare mesoporous titania (meso-TiO2), and finally used the impregnation method to generate the RuxMny/meso-TiO2 (Ru loading = 0.60–0.79 wt%) catalysts. Various techniques were used to measure physicochemical properties of the samples, and their catalytic performance was determined for methyl ethyl ketone (MEK) oxidation. It is found that the RuxMny/meso-TiO2 samples possessed a three-dimensionally ordered mesoporous structure, a surface area of 71–173 m2/g, and a uniform RuxMny particle size of 2.3–2.9 nm. Among all of the samples, Ru25Mn21/meso-TiO2 exhibited the best catalytic performance and good hydrothermal stability: the temperatures at MEK conversions of 10, 50, and 90 % were 131, 226, and 248 °C at a space velocity of 20,000 mL/(g h), with the apparent activation energy, specific reaction rate at 160 °C, and turnover frequency (TOF) at 160 °C being 73 kJ/mol, 41.73 mmol/(gRu s), and 4.20 s−1, respectively. In addition, introduction of 5 vol% moisture to the reaction system exerted a positive effect on catalytic activity of Ru/meso-TiO2 or Ru25Mn21/meso-TiO2 at higher temperatures. Such good performance of the Ru25Mn21/meso-TiO2 sample was related to its well dispersed Ru25Mn21 nanoparticles, high adsorbed oxygen species concentration, active surface lattice oxygen, high MEK adsorption capacity, good redox ability, and strong interaction between Ru25Mn21 and meso-TiO2. We propose that MEK might be oxidized by the adsorbed oxygen and/or surface lattice oxygen species via in turn formation of 2,3-butanedione, acetaldehyde, acetic acid, formaldehyde, and formic acid, all of which were finally converted to water and carbon dioxide.

The design and synthesis of g-C3N4 with favourable physical-chemical architecture are important factors in influencing its photoactivity. Herein, a phosphorus (P) vapor assisted synthetic strategy was employed to fabricate the P-doped hollow g-C3N4 photocatalysts with ultrathin shell structure (

In this work, we constructed a red phosphorus (RP)/TiO2 composite system via a chemical vapor deposition strategy. The evolution of the fibrous phased RP nanorods on the surface of anatase TiO2 spheres was rationally adjusted by controlling the composition of precursors. The optimal RP/TiO2 composite exhibited a significantly enhanced visible-light-driven photocatalytic H2 generation rate of 681 μmol h−1 g−1. The tightly interior surface bonding between RP and TiO2 greatly promoted the efficient charge transfer and redistribution by suppressing the charge recombination and self-trapping processes within TiO2, resulting in prolonged lifetimes of the active charges during the photocatalytic process as investigated in detailed using femtosecond time-resolved transient absorption (fs-TA) spectroscopy.

Catalytic oxidation is one of the effective pathways for completely eliminating volatile organic compounds (VOCs) emitted from industrial and transportation activities. Meanwhile, single-atom catalysts have excellent application prospects in numerous reactions due to their high metal atomic utilization efficiency. In this work, we adopted a novel strategy to prepare an active Pd/Co single-atom catalyst (i.e., Pd1Co1/Al2O3) for benzene oxidation. The successful formation of the atomically dispersed palladium and cobalt species on Al2O3 was verified by the aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure. By the in situ temperature-programmed techniques and in situ diffuse reflectance Fourier transform infrared spectroscopy, we observed a double effect of the palladium and cobalt oxide active sites, resulting in an enhanced performance for benzene oxidation. A benzene conversion of 90 % was achieved over the Pd1Co1/Al2O3 catalyst at 250 °C and a space velocity of 40,000 mL/(g h). Interestingly, the catalyst also possessed enhanced sulfur resistance performance. The good regeneration ability of the active sites in the catalyst was due to the single-atom dispersion of Pd and Co. In addition, we deduce that benzene oxidation might occur over Pd1Co1/Al2O3 via a pathway of benzene → cyclohexadiene → phenol → quinone → maleate → acetate → CO2 and H2O. We believe that the obtained results can provide a useful idea for rationally designing the double active site single-atom catalysts and understanding the mechanism of VOCs oxidation.

The nature of porous support (mesoporous Al2O3 and MgO (denoted as meso-Al2O3 and meso-MgO, respectively) and microporous HZSM-5) on catalytic performance of the bimetallic RuCo nanoparticles (NPs) was investigated for the oxidation of 1,2-dichloroethane (1,2-DCE). Redox and acid properties and reaction intermediates of the samples were measured by means of various techniques. The RuO2 species were dominantly present in the supported bimetallic samples, and Co doping could increase the length of the Ru−O bond. Compared with RuCo/meso-MgO and RuCo/meso-Al2O3, RuCo/HZSM-5 exhibited the highest catalytic activity (T90% =281 °C, TOFNoble metal = 3.6 × 10−3 s−1, reaction rate at 270 °C = 18.7 μmol/(gNoble metal s), and apparent activation energy =36 kJ/mol at SV = 20,000 mL/(g h)) and the best Cl-resistant performance, which was associated with its strong redox ability, suitable acidity, good 1,2-DCE adsorption capacity, highly dispersed RuCo NPs, and strong interaction between RuCo NPs and HZSM-5. Loading of RuCo NPs on the support could suppress the formation of C2H3Cl and improve the Cl-resistant performance. Over the RuCo/HZSM-5 sample, the partial deactivation induced by water vapor or HCl addition was reversible, while that induced by SO2 introduction was irreversible. Based on the characterization results, we believe that the oxidation of 1,2-DCE over RuCo/meso-Al2O3, RuCo/meso-MgO or RuCo/HZSM-5 might take place concurrently via the Langmuir−Hinshelwood and Mars−van Krevelen mechanisms. This work can provide a strategy to develop the efficient catalysts with low Cl-containing by-products formation, high CO2 selectivity, and good Cl-resistance in the oxidative removal of Cl-VOCs under the practical conditions.

Palladium-based catalysts are highly active for eliminating volatile organic compounds. Reducing the use of noble metals and enhancing performance of a catalyst are always desirable. The three-dimensionally ordered macroporous (3DOM) Mn2O3-supported transition metal M (M = Mn, Cr, Fe, and Co)-doped Au–Pd nanoparticles (NPs) with an Au–Pd–xM loading of 1.86–1.97 wt% were prepared using the modified polyvinyl alcohol-protected reduction method. It is found that the Au–Pd–xM NPs with a size of 3.6–4.4 nm were highly dispersed on the surface of 3DOM Mn2O3. The 1.94 wt% Au–Pd–0.21Co/3DOM Mn2O3 and 1.94 wt% Au–Pd–0.22Fe/3DOM Mn2O3 samples performed the best for the oxidation of methane and o-xylene, respectively. The methane oxidation rate at 340 °C (339.0 × 10−6 mol/(gPd s)) over 1.94 wt% Au–Pd–0.21Co/3DOM Mn2O3 was three times higher than that (93.8 × 10−6 mol/(gPd s)) over 1.97 wt% Au–Pd/3DOM Mn2O3, and the o-xylene reaction rate at 140 °C (2.59 μmol/(gN s) over 1.94 wt% Au–Pd–0.22Fe/3DOM Mn2O3 was two times higher than that (0.93 μmol/(gN s) over 1.97 wt% Au–Pd/3DOM Mn2O3. It is concluded that doping a certain amount of the transition metal to Au–Pd/3DOM Mn2O3 could modify the microstructure of the alloy NPs, thus improving the oxygen activation and methane adsorption ability. We are sure that the M-doped Au–Pd/3DOM Mn2O3 materials are promising catalysts for the efficient removal of volatile organic compounds.

The three-dimensionally ordered macroporous (3DOM) BiVO 4 and its supported iron oxide ( x Fe 2 O 3 /3DOM BiVO 4 , x = 0.18, 0.97, and 3.40 wt%) photocatalysts were prepared using the ascorbic acid-assisted polymethyl methacrylate-templating and incipient wetness impregnation methods, respectively. Physicochemical properties of the materials were characterized by means of numerous analytical techniques, and their photocatalytic activities were evaluated for the degradation of 4-nitrophenol under visible light illumination. It is found that the BiVO 4 possessed a high-quality 3DOM architecture with a monoclinic crystal phase, and the Fe 2 O 3 was highly dispersed on the surface of 3DOM BiVO 4 . The x Fe 2 O 3 /3DOM BiVO 4 samples much outperformed the 3DOM BiVO 4 sample, and 0.97Fe 2 O 3 /3DOM BiVO 4 showed the best photocatalytic performance (98% 4-nitrophenol was degraded in the presence of 0.6 mL H 2 O 2 within 30 min of visible light illumination) and excellent photocatalytic stability. The introduction of H 2 O 2 to the reaction system could promote the photodegradation of 4-nitrophenol by providing the active OH species generated via the reaction of photoinduced electrons and H 2 O 2 . The pseudo-first-order reaction rate constants (0.0876–0.1295 min −1 ) obtained over x Fe 2 O 3 /3DOM BiVO 4 were much higher than those (0.0033–0.0395 min −1 ) obtained over 3DOM or Bulk BiVO 4 and Fe 2 O 3 /Bulk BiVO 4 , with the 0.97Fe 2 O 3 /3DOM BiVO 4 sample exhibiting the highest rate constant. The enhanced photocatalytic performance of 0.97Fe 2 O 3 /3DOM BiVO 4 was associated with its unique porous architecture, high surface area, Fe 2 O 3 − BiVO 4 heterojunction, good light-harvesting ability, high adsorbed oxygen species concentration, and excellent separation efficiency of photogenerated electrons and holes as well as the photo-Fenton degradation process.

We prepare α-Fe2O3 nanosheet supported 0.38, 0.81, and 1.36 wt% Au (average particle size = 4.0 nm) nanocatalysts, and investigate their performance and mechanism for the selective catalytic oxidation of isopropanol to acetone. In the presence of 1.2 vol% isopropanol and 40 vol% O2, 1.36 wt% Au/α-Fe2O3 exhibits excellent catalytic performance, due to its moderate acidic sites and better redox properties, with acetone selectivity and yield being as high as 99% and 95% at 220 oC, respectively. In addition to acetone, little propylene, acetic acid, acetaldehyde, methyl vinyl ketone, 2-butanone, isopropyl ether, isopropyl acetate, 3-penten-2-one, isopropyl acrylate, isopropyl propionate, and 2, 4-dimethylfuran are detected. The possible reaction mechanism is proposed for the selective catalytic oxidation of isopropanol to acetone over the present catalysts. We believe the present selective catalytic oxidation method, rather than the traditional complete catalytic oxidation method, provides an alternative and economic method for VOCs emissions control.

We prepare TiO2 nanosheet-supported Pt nanocatalysts with an average size of 1.3, 1.9, and 3.0 nm. Due to the great decrease in the adsorption ability for toluene and acetone, mutual inhibition is first observed over Pt1.9 nm/TiO2 for the catalytic removal of a toluene and acetone mixture. At 140 °C, the toluene and acetone reaction rate is 0.033 and 0.045 μmol/(gcat s), respectively, for the oxidation of 500 ppm toluene or acetone, which is much higher than the corresponding reaction rate (0.020 and 0.007 μmol/(gcat s)) for the oxidation of the mixture. Pt1.9 nm/TiO2 exhibits a good catalytic stability and H2O and CO2 tolerance. With strong evidence, we find that the co-presence of toluene and acetone does not change the catalytic mechanism, and the reaction pathway for the oxidative removal of toluene and acetone in the mixture may follow the pathway for the oxidation of single toluene or acetone.

The three-dimensionally ordered macroporous (3DOM) CeO2-supported Au–Pd alloys (xAuPdy/3DOM CeO2, x is the total loading (wt%) of Au and Pd, and y is the Pd/Au molar ratio) were synthesized using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods. The samples were characterized by a number of analytical techniques, and their catalytic performance was evaluated for the combustion of trichloroethylene (TCE). It is found that the xAuPdy/3DOM CeO2 samples displayed a good-quality 3DOM architecture, and the noble metal nanoparticles (NPs) with a size of 3–4 nm were uniformly dispersed on the skeleton surface of 3DOM CeO2. Among all of the samples, 2.85AuPd1.87/3DOM CeO2 exhibited the highest catalytic activity, with the temperature at a TCE conversion of 90% (T90%) being 415 °C at a space velocity of 20,000 mL/(g h). Furthermore, the 2.85AuPd1.87/3DOM CeO2 sample possessed the lowest apparent activation energy (33 kJ/mol), excellent catalytic stability, and good moisture- and chlorine-tolerant behaviors. Alloying of Au with Pd changed the pathway of TCE oxidation and reduced formation of perchloroethylene. We conclude that the excellent catalytic performance for TCE combustion of 2.85AuPd1.87/3DOM CeO2 was associated with the highly dispersed AuPd1.87 alloy NPs, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between AuPd1.87 NPs and 3DOM CeO2 as well as the high-quality 3DOM structure and high surface acidity.

Polymethyl methacrylate-templating and ethylene glycol reduction methods were adopted to prepare the nanosized Pt catalysts (x wt% Pt/3DOM Mn2O3; x = 0.2–2.3) that were partially embedded in the skeleton of three-dimensionally ordered macroporous (3DOM) Mn2O3. These materials possessed a surface area of 33–36 m2/g, with the Pt NPs (3.6–4.4 nm in size) being well embedded in the skeleton of 3DOM Mn2O3. The 2.3 wt% Pt/3DOM Mn2O3 sample showed the best activity and the lowest apparent activation energy (41 kJ/mol) for toluene combustion, which was related to its high adsorbed oxygen species concentration and good low-temperature reducibility. Compared with 2.0 wt% Pt/3DOM Mn2O3-imp derived from the colloid adsorption method, 2.3 wt% Pt/3DOM Mn2O3 exhibited a better catalytic stability within 60 h of toluene combustion. After calcination at 650 °C for 3 h, the average particle size of Pt nanoparticles (NPs) in 2.3 wt% Pt/3DOM Mn2O3 grew up slightly from 4.3 to 4.9 nm and toluene conversions decreased slightly, while that of Pt NPs in 2.0 wt% Pt/3DOM Mn2O3-imp increased greatly from 4.4 to 13.7 nm and toluene conversions dropped significantly. Effects of H2O, CO2, and SO2 on activity of 2.3 wt% Pt/3DOM Mn2O3 and 2.0 wt% Pt/3DOM Mn2O3-imp were also examined. Partial deactivation induced by H2O or CO2 addition was reversible, whereas that due to SO2 introduction was irreversible. It is concluded that the strong interaction between Pt NPs and 3DOM Mn2O3 was responsible for excellent stability of the partially Pt-embedded 3DOM Mn2O3 sample in toluene combustion.

Three-dimensionally ordered macroporous (3DOM) photocatalysts BiVO4 (denoted as 3D-BiV), AgBr/3D-BiV, and 0.17 wt% M/AgBr/3D-BiV (M Au, Pt, and Pd) were prepared using the polymethyl methacrylate-templating, low-temperature deposition, and polyvinyl alcohol-protected reduction methods, respectively. The as-prepared BiVO4 possessed a good-quality 3DOM structure and a high surface area. It is found that the AgBr and noble metals were uniformly distributed on the surface of 3D-BiV. Among the M/AgBr/3D-BiV samples, the 0.17 wt% Pd/AgBr/3D-BiV sample showed the highest photocatalytic activity for the degradation of 4-chlorophenol (4-CP) under visible light illumination (i.e., complete 4-CP degradation could be achieved within 150 min), which was associated with its good 3DOM structure, high surface oxygen adspecies concentration, easy transfer and separation of photogenerated carriers, and synergistic effect between AgBr or Pd nanoclusters and BiVO4.

Three-dimensionally ordered macroporous (3DOM) InVO 4 –BiVO 4 (InBi-3D) and its supported noble metal M nanoparticles ( x M/InBi-3D; x = 0.08–0.13 wt%; M = Au, Ag, Pd, Pt) were prepared using the polymethyl methacrylate-templating and polyvinyl alcohol- or polyvinyl pyrrolidone-assisted reduction methods, respectively. Physical properties of the materials were characterized by a number of analytical techniques. Photocatalytic activities of the x M/InBi-3D samples were evaluated for the degradation of rhodamine B (RhB), methylene blue (MB), and their mixture. It is found that the as-fabricated samples possessed a surface area of 17–30 m 2 /g, a M particle size of 2.5–3.8 nm, and a bandgap energy of 2.50–2.56 eV. The x M/InBi-3D photocatalysts showed high activities for the degradation of RhB, MB, and RhB + MB in the presence of a small amount of H 2 O 2 under visible-light irradiation, among which complete degradation of RhB, MB, and RhB + MB was achieved within 50, 90, and 120 min over 0.08 wt% Au/InBi-3D, respectively. The degradation of MB and RhB fellow the zero- and first-order reaction mechanisms with respect to dye concentration, respectively. It is concluded that the high photocatalytic efficiency of the Au-loaded sample in the removal of organic dyes was associated with its high surface area, high-quality 3DOM hierarchical architecture, InVO 4 –BiVO 4 composite, and high dispersion of gold nanoparticles.

Rhombohedrally crystallized three-dimensionally ordered macroporous (3DOM) LaMnO3 supported MnOx (5, 8, 12, 16 wt% MnOx/3DOM LaMnO3) catalysts were prepared using the in situ tryptophan-assisted poly(methyl methacrylate)-templating strategy. Physicochemical properties of the materials were characterized by means of numerous analytical techniques, and their catalytic activities were evaluated for the combustion of toluene and methanol. It is shown that the MnOx/3DOM LaMnO3 samples displayed a 3DOM architecture and a high surface area of 19–31 m2/g. The 12 wt% MnOx/3DOM LaMnO3 sample showed the highest oxygen adspecies concentration and the best low-temperature reducibility as well as the highly dispersed MnOx particles on the LaMnO3 surface, giving the highest TOF values of 7.9 x 10−6 s−1 for toluene combustion at 160 °C and 7.3 x 10−6 s−1 for methanol combustion at 80 °C. The apparent activation energies of the MnOx/3DOM LaMnO3 catalysts were 61–62 and 48–54 kJ/mol for toluene and methanol combustion, respectively. It is concluded that the excellent catalytic performance of 12 wt% MnOx/3DOM LaMnO3 was associated with its highest oxygen adspecies concentration, best low-temperature reducibility, and strong interaction between MnOx and 3DOM LaMnO3.

Rhombohedrally crystallized chain-like LaMnO3 and its supported gold (xAu/LaMnO3; x = 1.4, 3.1, and 4.9 wt%) catalysts have been prepared using the poly(ethylene glycol)-assisted polymethyl methacrylate-templating and gas bubble-assisted polyvinyl alcohol-protected reduction methods, respectively. It is shown that there were good correlations of surface adsorbed oxygen species concentration and low-temperature reducibility with catalytic activity of the samples for the oxidation of CO and toluene. Among the LaMnO3 and xAu/LaMnO3 samples, 4.9Au/LaMnO3 performed the best, giving the T50% and T90% of 61 and 91 °C for CO oxidation, and of 201 and 226 °C for toluene combustion, respectively. The apparent activation energies (29–50 and 47–62 kJ/mol) of the chain-like LaMnO3 and xAu/LaMnO3 samples were much smaller than those (63 and 97 kJ/mol) of the bulk LaMnO3 sample for the oxidation of CO and toluene, respectively. We believe that the higher surface area and oxygen adspecies concentration and better low-temperature reducibility as well as the strong interaction between Au nanoparticles and chain-like LaMnO3 support might account for the high catalytic performance of 4.9Au/LaMnO3.

Three-dimensionally ordered macroporous (3DOM) Eu0.6Sr0.4FeO3-supported cobalt oxide nanocatalysts (yCoOx/3DOM-ESFO; y wt% = 1, 3, 6, and 10) were prepared using the incipient wetness impregnation method. Physicochemical properties of the composite materials were characterized by means of numerous techniques, and their catalytic performance was evaluated for the combustion of toluene. It is shown that all of the samples displayed a well-defined 3DOM architecture with a surface area of 22–31 m2 g−1 and the loaded cobalt oxide nanoparticles with a diameter of 7–11 nm were well dispersed on the surface of the 3DOM-ESFO support. Among the yCoOx/3DOM-ESFO samples, the 3CoOx/3DOM-ESFO and 6CoOx/3DOM-ESFO ones possessed the highest oxygen adspecies concentration and the best reducibility at low temperature, and hence showing the best catalytic performance (the temperatures required for 50 and 90% toluene conversions were ca. 250 and 270 °C at a space velocity of 20,000 mL g–1 h–1, respectively) for toluene combustion. The apparent activation energies (ca. 72 kJ mol−1) of 3CoOx/3DOM-ESFO and 6CoOx/3DOM-ESFO were lower than that (81 kJ mol−1) of 3DOM-ESFO. It is concluded that the enhanced catalytic performance of 3CoOx/3DOM-ESFO and 6CoOx/3DOM-ESFO for toluene combustion was mainly related to their higher oxygen adspecies concentrations, stronger reducibility at low temperature, and better dispersion of cobalt oxide nanoparticles.

Rhombohedrally crystallized three-dimensionally ordered macroporous (3DOM) perovskite-type oxides LaMnO 3 with mesoporous skeletons were prepared using the poly(ethylene glycol) (PEG)- and/or l- lysine-assisted poly(methyl methacrylate) (PMMA)-templating method. Physicochemical properties of the materials were characterized by numerous analytical techniques. Catalytic performance of the as-prepared LaMnO 3 samples was evaluated for the combustion of toluene. It is found that addition of appropriate amounts of PEG400 and l- lysine was beneficial for the generation of high-quality 3DOM-structured LaMnO 3 (denoted as LaMnO 3 -PL-1, LaMnO 3 -PL-2, and LaMnO 3 -PL-3 derived with a PEG400/ l- lysine molar ratio of 1.23, 0.61, and 0.31, respectively) with mesoporous skeletons and high surface areas (32–38 m 2 /g). Among the LaMnO 3 samples, the LaMnO 3 -PL-2 one possessed the largest surface area and the highest contents of surface Mn 4+ and adsorbed oxygen species. 3DOM-structured LaMnO 3 showed better low-temperature reducibility than bulk LaMnO 3 , with the LaMnO 3 -PL-2 sample displaying the best low-temperature reducibility. Under the conditions of toluene concentration = 1000 ppm, toluene/O 2 molar ratio = 1/400, and space velocity = 20,000 mL/(g h), the porous LaMnO 3 catalysts remarkably outperformed the nonporous bulk counterpart; over the best-performing LaMnO 3 -PL-2 catalyst, the temperatures required for toluene conversion = 50 and 90% were ca. 226 and 249 °C, respectively. The apparent activation energies (58–61 kJ/mol) for toluene combustion over the LaMnO 3 -PL-1–3 catalysts were much lower than that (97 kJ/mol) over the bulk LaMnO 3 catalyst. It is concluded that the large surface area, high oxygen adspecies content, good low-temperature reducibility, and unique bimodal pore structure were responsible for the good performance of 3DOM-architectured LaMnO 3 with mesoporous skeletons for toluene combustion.

Bismuth vanadates with multiple morphologies and/or porous structures were prepared using the alcoho-hydrothermal strategy with bismuth nitrate and ammonium metavanadate as metal source, NaOH as pH adjustor, ethanol and ethylene glycol as solvent, and/or dodecylamine (DA), oleylamine (OL) or oleic acid (OA) as surfactant. The materials were characterized by means of the XRD, Raman, TGA/DSC, FT-IR, BET, SEM, TEM, XPS, and UV–vis techniques. The photocatalytic performance of the as-obtained samples was evaluated for the degradation of phenol in the presence of a small amount of H 2 O 2 under visible-light irradiation, and the effect of phenol concentration on the photocatalytic activity was also examined. It is found that the surfactant and pH value had a significant influence on the particle morphology and even the crystalline structure of the product. Porous olive-like monoclinic BiVO 4 samples could be prepared with DA, OL or OA as surfactant at pH = 1.5 or 3.0 and alcoho-hydrothermal temperature = 100 °C. With DA as surfactant at an alcoho-hydrothermal temperature of 100 °C, short-rod-like monoclinic BiVO 4 and porous sheet-layered spherical orthorhombic Bi 4 V 2 O 11 were obtained when the pH value of the precursor solution was raised to 7.0 and 11.0, respectively. Among the BiVO 4 samples, the porous olive-like one with a surface area of 12.7 m 2 /g exhibited the best visible-light-driven photocatalytic performance for phenol degradation. It is concluded that the excellent photocatalytic activity of the porous olive-like BiVO 4 sample was associated with its higher surface area and surface oxygen vacancy density, porous structure, lower bandgap energy, and unique morphology.

Rhombohedral chromia with three-dimensionally (3D) ordered mesopore structures were fabricated adopting the ultrasound-assisted nanocasting strategy with 3D ordered mesoporous silica (KIT-6) as hard template and chromium nitrate as metal source. The physicochemical properties of the materials were characterized by the XRD, TGA/DSC, BET, TEM/SAED, XPS, and H2-TPR techniques, and their catalytic activities were evaluated for the oxidation of typical volatile organic compounds (VOCs), such as formaldehyde, acetone, and methanol. It is found that there were tri-, penta-, and hexavalent chromium ions in the 3D mesoporous structure. Compared to the bulk chromia, the mesoporous chromia materials were larger in surface area (69–124 m2/g) and could be reduced at lower temperatures. Among the chromia catalysts, the meso-Cr-400 one obtained after calcination at 400 °C showed the best performance. Over meso-Cr-400 at space velocity = 30,000 mL/(g h), formaldehyde, acetone, and methanol conversions achieved 90% at 117, 124, and 130 °C, respectively; the corresponding apparent activation energies were 45.6, 49.7, and 50.8 kJ/mol. It is concluded that the ultrasound treatment was a key step to improve the mesoporosity quality of the chromia materials during the nanocasting process, and the factors, such as low-temperature reducibility, 3D ordered mesoporous architecture, and high-surface area, were responsible for the excellent catalytic performance of meso-Cr-400.

Single-phase perovskite-like oxides NdSrCu1−xCoxO4−δ and Sm1.8Ce0.2Cu1−xCoxO4+δ (x = 0, 0.2, and 0.4) were prepared using the citric acid complexing method coupled with ultrasonic treatment. We characterized the materials by a number of analytical techniques. It was found that the NdSrCu1−xCoxO4−δ and Sm1.8Ce0.2Cu1−xCoxO4+δ catalysts possess T and T′ crystal structures, respectively. There are Cu3+/Cu2+ ions and oxygen vacancies in the former and Cu2+/Cu+ ions and extra (over-stoichiometric) oxygen in the latter. We examined the catalytic activity of the materials for methane combustion. Methane conversion increased with a rise in the amount of nonstoichiometric oxygen over the two series of catalysts. It is concluded that oxygen nonstoichiometry and Cu3+/Cu2+ or Cu2+/Cu+ redox couples facilitate the oxidation of methane over the NdSrCu1−xCoxO4−δ and Sm1.8Ce0.2Cu1−xCoxO4+δ catalysts.